Infant Neuromotor Development and Neuropsychiatric Problems Modern Epidemiological approaches

markdownabstract__Background:__ This thesis focuses on the role of infant neuromotor development in relation to neuropsychiatric problems. I performed genetic studies to further our understanding of the association between neuromotor development in infancy and behavioral problems in childhood. Methods: Studies described in this thesis were performed in Generation R, a large prospective population-based cohort in Rotterdam, the Netherlands. In a large ample of children at age 9-20 weeks, 15 research assistants assessed neuromotor development (tone, responses, senses and other observations) using Touwen instrument. Parents reported on their behavior during childhood and cognitive abilities were observed at age 6 years. __Objectives:__ The aims of this thesis were 1) to study the associations between neuromotor development during infancy and childhood behavior and cognitive functioning, 2) to examine the extend to which genetic susceptibility for psychiatric disorders influences neuromotor development 3) to understand the role of infant neuromotor development in the association of genetic susceptibility for psychiatric disorders with behavioral outcomes during childhood. __Results:__ I showed that infant neuromotor development is associated with shifting and cold, but not hot executive functioning, as well as with autistic symptoms. I further found that infant neuromotor development (low muscle tone and senses) predicts internalizing, but not externalizing symptoms during childhood. Problems in shifting partly mediated association between low muscle tone and later internalizing symptoms. Furthermore, a higher genetic risk for schizophrenia and a lower genetic risk for bipolar disorder was associated with non-optimal overall neuromotor development during infancy. I also found that the genetic risk for autism spectrum disorder (ASD) predicts non-optimal neuromotor development and in particular low muscle tone, while the genetic risk for attention-deficit/hyperactivity disorder (ADHD) predicts non-optimal senses and other observations in boys. Infant neuromotor development mediates the association of genetic risk for ASD and ADHD with autistic symptoms. In particular, low muscle tone mediates the association of genetic risk for ASD with autistic symptoms, while senses and other observations mediate association of genetic risk for ASD and ADHD with autistic symptoms. __Conclusion:__ Early identification of non-optimal neuromotor development in infants with a high genetic risk, followed by early intervention, could potentially reduce autistic symptoms in children.